HEALTH ENCYCLOPEDIA

Lumbar Puncture

What is a lumbar puncture?

A lumbar puncture is sometimes called a "spinal tap." It’s a medical
procedure that can involve collecting a sample of cerebrospinal fluid (CSF). CSF
is the fluid that surrounds your spinal cord and brain. A laboratory can test
it for signs of certain medical conditions and infections.

When
is a lumbar puncture used?

Your doctor may order a lumbar puncture for a few different reasons. They
may use it to check for signs of certain medical conditions, such as:

meningitis

myelitis

demyelinating diseases, such as multiple
sclerosis

cancers that can affect your spinal cord and
brain

subarachnoid hemorrhage

In some cases, they may use a lumbar puncture to administer
medication directly into your spinal canal. For example, they may use it to give
you chemotherapy drugs.

What are the benefits of a lumbar puncture?

A lumbar puncture can help your doctor accurately diagnose or rule out
certain medical conditions, including some life-threatening illnesses. The quicker
they make a diagnosis, the sooner you can get appropriate treatment. Some
conditions, such as bacterial meningitis, can be fatal if you don’t get
treatment for them quickly enough.

A lumbar puncture can also help your doctor give you some types of
medication.

What
are the risks of a lumbar puncture?

A lumbar puncture is generally considered safe, but it can involve some
risks. According to the Mayo
Clinic, up to a quarter of people who get a lumbar puncture develop a
headache afterward. Lying down for a few hours after the procedure may lower
your risk of getting a headache.

Other potential risks include tenderness or pain in your lower back and
bleeding near the puncture site. You may experience some pain and numbness that
shoots down your legs. In rare cases, people experience brainstem herniation,
which is the movement of brain tissue from its normal position in your skull.
This is uncommon.

How should you
prepare for a lumbar puncture?

Tell your doctor about all of the medications you’re taking and ask them if
you should stop taking any of them before your lumbar puncture. For example,
they may advise you to stop taking blood thinners, such as aspirin or warfarin.

Your doctor may also order a CT or MRI scan before your lumbar puncture.
They can use it to check for signs of swelling around your brain or other
problems.

What
should you expect during a lumbar puncture?

Your doctor will conduct a lumbar puncture using a needle and syringe. They’ll
collect a sample of your spinal fluid in a tube attached to the syringe. Then,
they’ll send it to a laboratory for testing.

The procedure usually takes about 45 minutes. It usually includes the
following steps:

They’ll likely position you on your side.

They’ll clean your back with an antiseptic solution to
reduce your risk of infection and numb it with a local anesthetic.

They’ll inject a hollow needle into your subarachnoid
space to collect a sample of your CSF. You may feel some pressure at this
point, but the procedure usually isn’t painful.

After they remove the needle, they’ll clean and
bandage the puncture site.

For
a short period after the procedure, it’s likely they’ll monitor you for a headache,
dizziness, or other side effects.

What do the results
of a lumbar puncture mean?

They’ll
send the CSF sample to a lab for testing. Professionals in the lab may:

evaluate its appearance for cloudiness

check it for the presence
of protein and glucose

measure the level of red and white blood cell
levels it contains

check it for the presence of bacteria or viruses

It may take anywhere from a few hours to several days for them to analyze
your sample. Your doctor can help you understand what the results mean. They’ll
also advise you on any follow-up steps you should take.

What is the outlook?

Written by: MaryAnn DePietroMedically reviewed
on: Jun 21, 2016: University of Illinois-Chicago, College of Medicine

This feature is for informational purposes only and should not be used to replace the care and information received from your health care provider. Please consult a health care professional with any health concerns you may have.